Match src paths with aidl package name

In order for the build system to track updates to the header files
during incremental builds, always specify the src files using the same
path as the package for C++ compilations.

Bug: 112114177
Test: treehugger
Change-Id: I584f43a0386840ce3d066479e9e4035de81da144
diff --git a/cmds/idmap2/Android.bp b/cmds/idmap2/Android.bp
index 18d56fa..3bb9929 100644
--- a/cmds/idmap2/Android.bp
+++ b/cmds/idmap2/Android.bp
@@ -222,4 +222,5 @@
     srcs: [
         "idmap2d/aidl/android/os/IIdmap2.aidl",
     ],
+    path: "idmap2d/aidl",
 }